ruby module to encode and decode messages with a polybius square
The class PolybiusSQ is defined in lib/polybius_sq.rb
Exposed methods are PolybiusSq::encode and PolybiusSq::decode
Both take two args (one opt): input and replace (defaults to ["j", "i"])
Replace should be an array with 2 one-character strings and both encode and decode replace the first element with the second